Shares off Entergy (ETR), parent of Entergy New Orleans, closed Friday down 0.8% to $64.47 apiece after the announcement of its role in the 34-minute delay. Play was halted just after halftime in Sunday's NFL football game won by the Baltimore Ravens against the San Francisco 49ers.

Many TV viewers and game attendees had speculated that a dazzling display of fireworks during Beyoncé's halftime performance, might have played a role in the blackout. That turned out to be wrong.

During Friday's trading session, the stock price of New Orleans-based Entergy dropped more than 2%, but recovered more than half of that price decline before the closing bell.

Entergy said the power outage was traced to a faulty relay in switching gear designed to prevent a power failure in electric cables leading to the stadium. "During Sunday's game, the relay device triggered, signaling a switch to open when it should not have," the company said.

Company officials said the device performed without problem during January's Sugar Bowl and other earlier events. They said the device has been removed and replacement equipment will be installed.

Entergy officials disclosed information about the switching gear's failure as they prepared to answer questions about the outage from a committee of New Orleans' City Council members Friday. The council regulates the company.